Electron microscopy
 
Voltage Axis in TEM
- Practical Electron Microscopy and Database -
- An Online Book -
Microanalysis | EM Book                                                                                   http://www.globalsino.com/EM/        

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HT Wobbler in TEM mode is used to adjust the microscope optical axis to minimize the motion of the image, i.e. the image stays at the center of the fluorescent viewing screen even if the accelerating voltage is changed during TEM-imaging. This condition is converntionally called "Voltage Axis". This adjustment is normally done after the basic TEM alignments have been performed well. The typical steps for such Voltage Axis alignment is:
         i) Click the HT Wobbler (or called WOBBLER-HT) switch. While this switch is turned on, the high voltage varies periodically, facilitating alignment of the voltage axis.
         ii) Press the Bright Tilt (or called BRIT Tilt or Beam Tilt) switch, and then adjust the relavent knob(s), e.g. beam deflectors (DEF x and y) on some microscopes, to tilt the beam until the image expands and contracts around the center of the fluorescent screen.

 

 

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